1. Field of the Invention
The present invention relates to a process for producing an amorphous alloy forming material for the purpose of improving any amorphous alloy in its inherent embrittlement during high temperature working of the alloy in which the alloy is subjected to thermal hysteresis for a long time.
2. Description of the Prior Art
Some of the present inventors invented Al--transition metal element (hereinafter abbreviated as "TM")-rare earth metal element (hereinafter abbreviated as "Ln") alloys and Mg--TM--Ln alloys as lightweight high-strength amorphous alloys and applied for patents as Japanese Patent Laid-Open No. 275732/1989 and Japanese Patent application No. 220427/1988, respectively. Also, they invented Al--TM--Ln alloys and Zr--TM--Al alloys as alloys with high strength and excellent workability and applied for patents as Japanese Patent Application Laid-Open Nos. 36243/1991 and 158446/1991, respectively. Having high strength and high corrosion resistance, these alloys exhibit glass transition behavior and possess a supercooled liquid region, and therefore show favorable workability in the above region or at temperatures in the neighborhood of the region. Thus, these alloys obtained in the form of powder or thin strips can be easily subjected to consolidation-forming and cast into amorphous bulk material, which is also an excellent alloy showing good workability in the supercooled liquid region or at temperatures in the neighborhood thereof.
When maintained in the supercooled liquid region for a long time, however, the above-mentioned amorphous alloys begin to decompose into crystals, thus restricting the working time for consolidation-forming, working-forming, etc. As a means for avoiding the above problem, a method of consolidation-forming or working-forming at a temperature below the glass transition temperature is available. As is the case with general amorphous alloys, the alloys in question are characterized in that when heated to a high temperature region slightly below the glass transition temperature, they suddenly lose the ductility peculiar thereto and embrittle. Since the amorphous alloys that are subjected to consolidation-forming or reworking-forming at high-temperatures cannot sufficiently exhibit their inherent properties, an improvement in their properties has been desired.
It is known that an amorphous alloy generally embrittles when heated to high temperatures just below the glass transition temperature, even if lower than the crystallization temperature. The phenomenon is attributable to the structural change toward the more stable atomic configuration in spite of its being amorphous, and in general relates to the structural relaxation. The structural relaxation is in a state of reversible and irreversible reactions mixed with each other. Though the reversible reaction is canceled by rapidly heating to a high temperature, the structural relaxation takes place in an extremely short time, followed by another structural relaxation at another temperature, which is not preventable by simple reheating, and therefore is difficult to avoid.